Alternating-current motor.



H. ALEXANDER.

ALI'BBNATING CURRENT MOTOR.

APPLICATION FIL'ED JULY 21, 1909.

0 m w d m m P m 0 Z a m 5 F 9 Inventor Y Atty Wisnesses:

f m (fij i' W240 UNITED STATES PATENT OFFICE.

HANS ALEXANDER, 0F BERLIN, GERMANY, ASSIGNOB T0 GENERAL ELECTBIGCOMPANY. A CORPORATION OF NEW YORK.

ALTERNATING-CURRENT MOTOR.

Specification of Letters Patent.

Patented Mar. 29, 1910.

To all whom it may concern:

Be it known that I, Haws ALEXANDER, a subject of the Emperor of Germany,reslding-at Berlin, Germany, have invented certain new and usefulImprovements in Alternating-Current Motors, of which the following is aspecification.

1y invention relates to polvphase motors of the commutator type and itsobject is to improve the efliciency 0 such motors.

The stator winding of polyphase motors, as ordinarily arranged, is comosed of separate windings for the several phases, each distributed overa portion only of the stator. By the term separate I mean to distinguishthis type of winding from a single -closed winding with a poly )hasearrangement of terminals. The win ing with separate phases, eachdistributed over a portion 2Q only of the stator, produces a flat-toppedfield for each phase. ,VVhen, with such a stator winding,'the usualelectrically diametrical arrangement of commutator brushes is employed,the distributions ofstator and rotor magneto-motive forces are not thesame,the stator field being flattoppcd and the rotor being eaked. Thisdifference in distribution resui ts in leakage fields which have anunfavorable influence upon .the

torque, power-factor, and commutatioii. By

my invention such leakage fields are eliminated.

My invention consists in so arranging the commutator brushes and theirconnections that they form with the rotor winding polyphase circuitseach of which comprises a set of rotor conductors lying opposite theconductors of one of the phases of the stator Winding,-that is. thedistribution of the conductors comprising each rotor circuit correspondsto the distribution of stator conductors in each phase of the statorwinding,

so that the magnetomotive forces of stator and rotor are of the sameshape, and leakage fields are avoided.

zation along a vertical line, and the coils a? alon a horlzontal line.It will be seen that the ehl produced by each set of coils isflattopped. B represents the rotor and b a 1'0- tor coil, the othercoils being omitted to avoid confusing the dia ram. C represents thecommutator to whici the rotor coils are connected. b to I) represent thecommutator brushes placed in accordance with m invention. b to 6represent in dotted iines the usual positions of the brushes in such amotor,that is, the brushes 6 and b" are arranged diametrically oppositeon the line of magnetization of the stator phase a, and brushes b and bdiametrically opposite on the line of magnetization of the stator phasea It will be seen that with this usual arrangement of brushes indicatedby the dotted lines, the rotor fields are peaked, and consequentl do notcorrespond in shape to the stator elds. If, however, the brushes arearranged as shown in full lines at b to b, and circuits for one phaseformed to include the conductors between brushes 6 and b and theconductors between brushes 6 and b, the rotor conductors included inthis phase will lie opposite the conductors in the stator phase 0. and afiat-topped field will be )roduced of the same shape as that produced ythe coils a Similarly the portions of the rotor between brushes b and b,and between brushes 6 and b comprise the circuits for the other phase.

If a variable voltage is to be impressed on the rotor for speed control,the circuit arrangement maybe as shown in Fig. 2. Two transformers D andD have their primaries connected in parallel with the stator phase a andtheir secondaries connected across brushes b and 7)", and brushes b andb, respectively. The transformers D and D are similarly connected forthe other phase. The number of turns of the transformer secondaries isindicated as variable, so that the voltage impressed on the rotorcircuits may be varied to control the motor s eed.

If it is desired to vary the p ase, as well as the amount, of the rotorimpressed voltage, in order to improve the power-factor,

this may be accomplished.by the arrangement shown in Fig. 3. in whichthe circuit between each pair of brushes includes portions of twotransformer windings of different. phase. Thu for instance. the circuitbetween brushes 7) and If. in addition to including :1 Variable portionof the secondary oftransformer D includes a variable portion of thesecondary of transformer I).

I do not desire to limit myself to the particular construction andarrangement of parts here shown. but aim in the appended claims to coverall modifications which are within the scope of my invention.

\Vhat claim a new and desire to secure by Letters Patent of the UnitedStates, is,

1. it pol phase motor of the commutator type comprising a polyphasestator winding, each .phase compri ing a separate winding distributedover a portion only of the stator, a rotor winding provided with acommutator, and commutator brushes and connections forming with portionsof the rotor winding polyphase circuits, the brushes being so arrangedthat each rotor circuitcomprises a set of rotor conductors lying oposite the conductors of one of the phases 0 the stator winding.

2. A polyphase motor of the commutator type comprising-a polyphasestator winding. each phase comprising a separate winding distributedover a portion only of the stator, a rotor winding provided"with a commutator, commutator brushes and connections forming with portions of therotor winding polyphase circuits, the brushes being so arranged thateach rotor circuit comprises a set of rotor conductors lying oppositethe conductors of one of the phases of the stator winding, and sourcesof variable voltage included in the several rotor circuits. i

3. A. polyphase motor of the commutator type comprising a polyphasestator winding, each phase comprisin a separate winding distributed overa portion only of the stator,

a rotor windingprovided with a comnor ttttor. con'nnutator brushes andconnection forming with portions of the rotor winding polyphasecircuits. the brushes being so arranged that each rotor circuitcomprises a portion only of the rotor coils. which portion correspondsin amount and in position with the portion of the stator over which onephase of the stator windingis distributed.

,5. A polyphase motor of the commutator type comprising a polyphasestator winding. each phase comprising a separate winding distributedover a portion only of the lilitll'. a rotor winding provided with aCOIIIIHIP tator, commutator brushes and connections forming with therotor winding polyphase circuits, the brushes being so arranged thateach rotor circuit comprises a portion only of the rotor coils. whichportioncorresponds in amount and in position with the portion of thestator over which one phase of the stator winding is distributed. andseparate transformer windings of variable numbers of turns included inthe several rotor circuits.

. In witness whereof. I have hereunto tt my hand this'1'2 June, 1909.

' HANS ALEXANDER. \Vitnesses RICHARD T. DL'XAN, Josarn D. GRIFFIN.

